Style sheets are used to give a common look to a collection of documents such as web pages. With style sheets, the content of a document can be separated from its presentation. Cascading Style Sheets (CSS) extend the HyperText Markup Language (HTML) and enable the precise placement of HTML document elements and the precise selection of fonts in HTML documents. CSS can be used by a web page designer to give a common look and feel to large number of documents, and to provide fonts, spacing, aural cues, etc. to structured documents (e.g., HTML documents and XML applications). An Extensible Stylesheet Language (XSL) stylesheet specifies the presentation of a class of XML documents by describing how an instance of the class is transformed into an Extensible Markup Language (XML) document that uses the formatting vocabulary.
A service provider may host style sheets that specify how its user interface (UI) should look like. A third party reseller that sells services of the service provider to customers may want to customize these style sheets to change the presentation of the UI elements. For example, a third party reseller may want to add their logo to some web pages or change the background of the web pages. Currently, the third party reseller can customize the style sheets only if the third party reseller hosts all of the style sheets provided by the service provider. However, the service provider typically continues to evolve the UI, thus affecting the UI customizations already in place.